Stable Adsorption Structure Research Articles

Novel gas sensing mechanisms of Pd and Rh-doped h-BN monolayers for detecting dissolved gases (H2、CH4、and C2H4) in transformer oil

Detecting dissolved gases in transformer oil is crucial for assessing the operational status of transformers. The gas composition in transformer oil can reflect the health status of the equipment and help identify potential failure risks in a timely manner. Based on density functional theory (DFT), Pd and Rh atoms were doped into the h-BN monolayer, and the most stable adsorption structures for each were first explored. Then, the sensing performance of the Pd-doped and Rh-doped h-BN monolayers for H2, CH4, and C2H4 gases was analyzed. The results indicate that Pd-BN and Rh-BN exhibit enhanced sensitivity to H2 and C2H4 gases compared to pristine h-BN. However, they show poor adsorption characteristics for CH4. Both Pd-BN and Rh-BN demonstrate strong chemisorption for H2 and C2H4. In contrast, CH4 adsorption is predominantly physisorbed. The desorption time of H2 from Pd-BN at 398 K is 164 s, reflecting its excellent desorption performance. Additionally, Pd-BN and Rh-BN monolayers exhibit exceptional C2H4 capture capabilities, with adsorption energies of −1.697 eV and −2.188 eV, respectively, indicating their potential as C2H4 gas adsorbents. These findings provide theoretical insights for selecting materials for dissolved gas detection in oil and lay the groundwork for the development of Pd-BN and Rh-BN-based gas sensors.

Adsorption of molecular hydrogen (H2) on a fullerene (C60) surface: insights from density functional theory and molecular dynamics simulation.

Understanding the adsorption behavior of molecular hydrogen (H2) on solid surfaces is essential for a variety of technological applications, including hydrogen storage and catalysis. We examined the adsorption of H2 (∼2800 configurations) molecules on the surface of fullerene (C60) using a combined approach of density functional theory (DFT) and molecular dynamics (MD) simulations with an improved Lennard-Jones (ILJ) potential force field. First, we determined the adsorption energies and geometries of H2 on the C60 surface using DFT calculations. Calculations of the electronic structure help elucidate underlying mechanisms administrating the adsorption process by revealing how H2 molecules interact with the C60 surface. In addition, molecular dynamics simulations were performed to examine the dynamic behavior of H2 molecules on the C60 surface. We accurately depicted the intermolecular interactions between H2 and C60, as well as the collective behavior of adsorbed H2 molecules, using an ILJ potential force field. Our findings indicate that H2 molecules exhibit robust physisorption on the C60 surface, forming stable adsorption structures with favorable adsorption energies. Calculated adsorption energies and binding sites are useful for designing efficient hydrogen storage materials and comprehending the nature of hydrogen's interactions with carbon-based nanostructures. This research provides a comprehensive understanding of H2 adsorption on the C60 surface by combining the theoretical framework of DFT calculations with the dynamical perspective of MD simulations. The outcomes of the present research provide new insights into the fields of hydrogen storage and carbon-based nanomaterials, facilitating the development of efficient hydrogen storage systems and advancing the use of molecular hydrogen in a variety of applications.

Investigation into geometric configurations and electronic properties of CeO2-supported gold clusters

A detailed understanding of the geometric structure and electronic properties of gold nanoparticles on the ceria surface is crucial for comprehending their unique catalytic activity. Using the first-principles method based on density functional theory, the adsorption of Aux (x = 1–4) clusters on the CeO2(111) surface was studied. It was discovered that the standing configurations of Au2 and Au3, as well as the tetrahedral structure of Au4, are the most stable adsorption structures. The stability of these configurations is jointly determined by the number and strength of Au-Au bonds, the Au-O bonding energy, and the interaction dynamics between the clusters and the substrate. The analysis of Bader charge, difference charge density and density of states suggested that lattice relaxation and electronic localization occur in the reduced Ce3+. The reduced amount and location of Ce3+ are significantly influenced by the position and charge transfer amount of Aux cluster. The adsorption of CO on Au4/CeO2(111) indicated that stronger Au-C bonding energy due to the hybridization of Au-5d and C-2p, thereby enhancing the catalytic activity for CO oxidation reactions.

Effect of voltage gradients on EK-PRB remediation: Experimental and molecular dynamics simulations

Electrokinetic-Permeable Reaction Barrier (EK-PRB) coupled remediation technology can effectively treat heavy metal-contaminated soil near coal mines. This study was conducted on cadmium (Cd), a widely present element in the soil of the mining area. To investigate the impact of the voltage gradient on the remediation effect of EK-PRB, the changes in current, power consumption, pH, and Cd concentration content during the macroscopic experiment were analyzed. A three-dimensional visualized kaolinite-heavy metal-water simulation system was constructed and combined with the Molecular Dynamics (MD) simulations to elucidate the migration mechanism and binding active sites of Cd on the kaolinite (001) crystalline surface at the microscopic scale. The results showed that the voltage gradient positively correlates with the current, power consumption, and Cd concentration during EK-PRB remediation, and the average removal efficiency increases non-linearly with increasing voltage gradient. Considering power consumption, average removal efficiency, and cost-effectiveness, the voltage range is between 1.5 and 3.0 V/cm, with 2.5 V/cm being the optimal value. The results of MD simulations and experiments correspond to each other. Cd2+ formed a highly stable adsorption structure in contrast to the Al–O sheet on the kaolinite (001) crystalline surface. The mean square displacement (MSD) curve of Cd2+ under the electric field exhibits anisotropy, the total diffusion coefficient DTotal increases and the Cd2+ migration rate accelerates. The electric field influences the microstructure of Cd2+ complexes. With the enhancement of the voltage gradient, the complexation between Cd2+ and water molecules is enhanced, and the interaction between Cd2+ and Cl− in solution is weakened.

Adsorption Structures, Vibrational Raman Spectra and Chemical Binding Properties of Thioglycolic Acid on Cu(111) Surfaces: A DFT Study.

Copper is widely used in everyday life and industrial production because of its good electrical and thermal conductivity. To overcome copper oxidation and maintain its good physical properties, small organic molecules adsorbed on the surface of copper make a passivated layer to further avoid copper corrosion. In this work, we have investigated thioglycolic acid (TGA, another name is mercaptoacetic acid) adsorbed on copper surfaces by using density functional theory (DFT) calculations and a periodical slab model. We first get five stable adsorption structures, and the binding interaction between TGA and Cu(111) surfaces by using density of states (DOS), indicating that the most stable configuration adopts a triple-end binding model. Then, we analyze the vibrational Raman spectra of TGA adsorbed on the Cu(111) surface and make vibrational assignments according to the vibrational vectors. Finally, we explore the temperature effect of the thermodynamically Gibbs free energy of TGA on the Cu(111) surface and the antioxidant ability of the small organic molecular layer of copper oxidation on the copper surface. Our calculated results further provide evidences to interpret the stability of adsorption structures and antioxidant properties of copper.

Interactions of Acetylene-Derived Thioester Collectors with Gold Surfaces: A First-Principles Study

The high reactivity of the acetylene group enables the formation of strong chemical bonds with active sites on mineral surfaces, thereby improving the flotation performance of gold minerals. This study utilized density functional theory (DFT) to analyze the quantum chemical parameters of structure, Mulliken population, and the frontier orbitals of a thioester collector containing an acetylene group, PDEC (prop-2-yn-1-yl diethylcarbamodithioate). PDEC was compared with analogous thioester collectors Z-200 and Al-DECDT. The interaction mechanism of PDEC on the Au(1 1 1) surface was simulated, followed by empirical validation through adsorption experiments. The findings indicate that the S atom of PDEC in the carbon–sulfur group exhibits shorter covalent bond lengths, and has reduced carbon–sulfur double bonds and Mulliken population, resulting in enhanced electron localization. This confers greater selectivity to PDEC during its adsorption on mineral surfaces. Frontier orbital analysis shows that the electrons of the acetylene group possess a notable electron-accepting capacity, significantly influencing the frontier orbital energy of PDEC and playing a pivotal role in the bonding interaction with mineral surfaces. Both the S atom in the carbon–sulfur group and its acetylene group establish stable adsorption structures with the A(111) surface in a single coordination mode. The adsorption energy sequence is PDEC > Al-DECDT > Z-200. Partial density of states demonstrates that the S 3p orbit of the carbon–sulfur group hybridizes with the Au 5d orbit, while the C 2p orbit of the acetylene group engages in weaker back-donation bonding with the Au 5d orbit. This is corroborated by the electron density difference and post-adsorption Mulliken population analyses, revealing that the S atom of the carbon–sulfur group in PDEC donates electrons to the Au atom, forming dominant positive coordination bonds, whereas the acetylene group accepts partial electrons from the Au atom, resulting in weaker back-donation bonds. The adsorption experiments align with the DFT adsorption energy results.

First-principles studies of gas molecule adsorption on a LaB6(100) surface.

First-principles calculations were employed to study the molecular and dissociative adsorption of CO2, H2O, O2 and N2 on a LaB6(100) surface. The adsorption energy calculation results indicate that these gas molecules can form thermodynamically stable adsorption structures. Dissociative adsorption is always accompanied by more electron transfer compared to molecular adsorption, which is one of the necessary conditions for dissociation to occur. Bader charge analysis indicates that the adsorption of gas molecules on the LaB6(100) surface is always accompanied by electron transfer from the surface to the adsorbed molecules. This electron transfer forms a dipole moment from the adsorbed molecule towards the surface, leading to an increase in the work function of LaB6(100). This mechanism is a crucial aspect of the LaB6(100) poisoning effect. Additionally, LaB6(100) sometimes exhibits a certain degree of resistance to poisoning. In such cases, after the adsorption of gas molecules, local regions of the LaB6(100) surface become negatively charged, which counteracts the poisoning effect to some extent. Using electronic density of states and electron localization function analyses, we examined the nature of the chemical bonds. It was found that La tends to form non-covalent bonds with the adsorbates, whereas B tends to form covalent bonds with them. The 2p orbitals of B play a significant role in the formation of these covalent bonds in most cases.

Adsorption of NO2, NO, NH3, and CO on Noble Metal (Rh, Pd, Ag, Ir, Pt, Au)-Modified Hexagonal Boron Nitride Monolayers: A First-Principles Study.

To investigate the application of modified hexagonal boron nitride (h-BN) in the detection and monitoring of harmful gases (NO2, NO, NH3, and CO), first-principles calculations are applied to study the geometric structure and electronic behavior of the adsorption system. In this paper, the four adsorption sites, namely, B, N, bridge, and hollow sites, are considered to explore the stable adsorption structure of metals (M = Rh, Pd, Ag, Ir, Pt, and Au) on the BN surface. The calculation results demonstrate that the geometric structures of metal at the N-site are relatively stable. Subsequently, the different adsorption structures of NO2, NO, NH3, and CO on M-BN are researched. The electron transfer, charge difference density, and work function of the stable adsorption structure are calculated. The results show that NO2, NO, and CO have the strongest adsorption capacity in the Ir-BN system, with adsorption energies of -2.705, -5.064, and -3.757 eV, respectively. The Pt-BN system has an excellent adsorption performance (-2.251 eV) for NH3. Compared with the M-BN system, the work function of the adsorption system increases after adsorbing NO2, while it decreases after adsorbing NH3. This work shows that h-BN with metal modification is a potential material for online monitoring of harmful gases.

Theoretical investigation of outer-sphere adsorption of hydrated yttrium ion on the basal surfaces of kaolinite: A density functional study

Ion-adsorption deposits (IADs) are important types of REE deposits. Previous studies have found that, in IAD, REE3+ adsorb on the surface of clay minerals in the form of multi-coordinated hydrated complexes, [REE(H2O)8/9]3+, forming exchangeable outer-sphere adsorption complex. Actually, there are two types of basal surfaces in clay minerals, the (001) surface and the (00−1) surface, and it is not clear whether there are differences in the adsorptions on these two types. Additionally, the electron transfer mechanism in the adsorption structures cannot be revealed. To address these issues, we employ first-principles calculations based on density functional study to simulate the outer-sphere adsorption structures of representative Y3+ ion on the two types of basal surface of kaolinite. The study reveals that both the (001) surface and the (00–1) surface can serve as adsorption surfaces, but the (00–1) surface forms more stable adsorption structures with adsorbate-[Y(H2O)8]3+ due to the absence of hydroxyl group repulsion effects. The adsorption process involves electron transfer from the kaolinite basal surface to the adsorbate, forming hydrogen bonds. The primary orbital interaction in this process is between the O-2p orbitals of the adsorbate and the surface O-2p orbitals. This work contributes to a quantum-level understanding of the nature of ion adsorption in ion-adsorption deposit.

Adsorption and sensing performances of air decomposition components (CO, NOx) on Cr modified graphene surface

The adsorption and sensing abilities of air decomposition components such as CO, NO, and NO2 on a Cr-graphene monolayer were investigated using the first principles of density functional theory. Firstly, three possible doping points of Cr atoms on the surface of graphene were studied, and the most stable Cr-graphene monolayer was obtained through modeling and computational analysis. Then, various adsorption structures were constructed and optimized based on the model. The most stable adsorption structure of Cr-graphene monolayer for the three characteristic gases was determined by comparing their adsorption energy and other relevant parameters.Furthermore, state density, differential charge, and molecular orbital theory analyze the gas sensing mechanism and desorption time. The results show that the surface of the pristine graphene has a weak adsorption effect on these gases, and the Cr-graphene monolayer has good adsorption performance for the three gases. Although the calculation results show that Cr-graphene monolayer has strong adsorption and gas sensitivity performance for the three components, the recovery performance of the Cr-graphene monolayer needs to be improved because of the immense adsorption energy of Cr-graphene monolayer for the three components. The calculation can provide a theoretical guidance for gas sensors based on graphene and its modified materials.

Role of imperfect coordination of amorphous metal oxide in its chemical reaction with epoxy resin in metal − polymer hybrid material

The chemical bonding between laser − induced metal oxide and polymer highly determines the interfacial bonding performance of metal − polymer hybrid materials. To achieve reliable interfacial chemical bonding, it is crucial to gain a molecular/atomic level understanding of the chemical reaction mechanism between the metal oxide and epoxy resin (main components of epoxy polymer). Previous research has demonstrated that laser ablation induces the formation of amorphous aluminium oxide on aluminium alloy surfaces. Our solid − state nuclear magnetic resonance (ssNMR) investigation reveals that this amorphous aluminium oxide is consisted mainly of 4 − fold and 5 − fold coordinated Al sites. Through an innovative combination of ssNMR and density functional theory calculations, this aluminium oxide was confirmed to form Al − O − C bonds with epoxy resin, preferentially at imperfectly coordinated Al sites due to active donor − acceptor interactions. It is clarified that imperfect coordination of amorphous aluminium oxide plays a more critical role than its amorphous nature in forming stable adsorption structure with epoxy resin. Furthermore, compared to on crystalline surface, 5 − fold coordinated Al site on amorphous surface exhibits higher reactivity, and the origin of activity is revealed through distortion/interaction analysis. This study provides a research guidance for further regulation and optimization of interfacial reactivity and bonding characteristics of metal − polymer hybrid materials.

Investigation of Hydrated Dy(III) and MgSO4 Leaching Agent Ion Adsorption on (001) Surface of Montmorillonite: A Study Using Density Functional Theory

Kaolinite is one of the principal rare earth element (REE) ion-adsorption clays that hosts a wide range of elements, including Dy(III) as a representative example. Ammonium sulfate is a typical salt used to leach REEs. Due to the carbon dioxide emissions which occur during ammonia production, it is urgently necessary to develop low environmental pollution leaching agents that can replace (NH4)2SO4. MgSO4 is regarded as the most promising eco-friendly leaching agent. Herein, the first-principles plane-wave pseudopotential method based on the density functional theory (DFT) was used to investigate the stable adsorption structures of Dy(III) and its hydrated ions, MgSO4 leaching agent ions and the corresponding hydrated ions on the surface of kaolinite, which revealed the adsorption mechanism of Dy(III), Mg(II), and SO42− on the silico–oxygen plane and the aluminum–hydroxyl plane of kaolinite. Based on the research results of the steric hindrance effect of Dy(III) on the silico–oxygen plane and the aluminum–hydroxyl plane of kaolinite, the adsorption of Dy(H2O)103+ was more stable on the silico–oxygen plane. It was easier to leach out Dy(III) with MgSO4, while SO42− tended to interact with the rare earth ions in an aqueous solution. The results provide theoretical guidance for efficient rare earth extraction and obtaining novel efficient leaching agents.

Insight into B S ratio model and surface atom interactions of co-doping diamond: First-principles studies

The complex co-doping structure of boron and sulfur is investigated using the density functional theory approach. Different ratio models show significant differences in electronic properties. More importantly, the interactions of boron, sulfur, and carbon atoms are studied on intrinsic/B-doped (001), (111), and (110) diamond surfaces. The most stable adsorption site, adsorption structure, and charge transfer are discussed. B atom induces a larger adsorption energy (intrinsic: −4.57 eV, −4.56 eV, and −4.00 eV; B-doped: −4.70 eV, −4.72 eV, and −4.86 eV). And a larger charge transfer between diamond and S radicals is also found. Therefore, the phenomenon that the sulfur contents in diamond increases after the introduction of boron in the experiment can be explained. Considering different crystal surfaces, larger adsorption strength is obtained from (111) and (110) surface. And different levels of strain are introduced into three different surfaces. The migration barrier of S atom is also considered. The lowest migration barrier is 0.06 eV on (111) surface, whereas the highest value is found on (001) surface (1.96 eV). B atom also benefits for the HxS radical adsorption. It can be concluded that B doping can help with S and HxS adsorption. This study can provide an explanation for the increased solubility of S on B-doped diamond.

The quantitative study of methane adsorption on the Pt(997) step surface as the initial process for reforming reactions

The adsorption states and thermal process of methane on a stepped Pt surface were investigated using temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), and density functional theory (DFT) calculations including van der Waals interactions. By estimating the activation energies of methane desorption from the TPD data, it was revealed that the adsorption energy for methane on the step site (0.19 eV) was higher than that on the terrace site (0.15 eV). The IRAS spectrum after multilayer adsorption and subsequent 70 K heating showed two peaks at 3009 and 1305 cm−1, which were assigned to the antisymmetric stretching and the deformation modes for adsorbed methane on the step site, respectively. The present DFT calculations show that the most stable adsorption structure for methane on the step site is a “2H” structure, where two C-H bonds point toward Pt atoms. Based on the electronic structure analysis, we conclude that the stability of the 2H structure originates from the mixing between the methane molecular orbitals and the orbitals of step Pt atoms. As a result, the length of the C-H bond pointing toward the Pt step atom is elongated compared with that of other C-H bonds. Thus, the Pt step site already activates the adsorbed methane slightly.

Multiple Pathways for Dissociative Adsorption of SiCl4 on the Si(100)-c(4×2) Surface

The adsorption of silicon tetrachloride (STC, SiCl4) on the silicon surface is a crucial process in polysilicon manufacture. However, the underlying mechanism for the adsorption remains highly uncertain. Here, new dissociative adsorption (DA) reaction pathways involving a flip of a silicon dimer in the first layer and considering physisorption are identified. Different DA patterns, inter-row (IR), inter-dimer (ID), and on-dimer (OD), are confirmed by the density functional theory (DFT) calculations at the PBE-D3(BJ)/TZVP-MOLOPT-GTH level. The stable structures for all minima are searched by global optimization through the artificial bee colony (ABC) algorithm. Findings reveal that the parent molecules dissociate first by breaking one Si-Cl bond, following which the resulting SiCl3 and Cl fragments are attached to adjacent Si-atom sites. Moreover, dimer flipping significantly reduces the energy barrier for chemisorption, mainly due to the change in electronic structure that enhances the interaction of the site with the SiCl3 radical. Physisorption may also be accompanied by dimer flipping to form a stable adsorption structure.

Elucidation of the mechanism of melamine adsorption on Pt(111) surface via density functional theory calculations.

The oxygen reduction reaction (ORR) activity of Pt catalysts in polymer electrolyte fuel cells (PEFCs) should be enhanced to reduce Pt usage. The adsorption of heteroaromatic ring compounds such as melamine on the Pt surface can enhance its catalytic activity. However, melamine adsorption on Pt and the consequent ORR enhancement mechanism remain unclear. In this study, we performed density functional theory calculations to determine the adsorption structures of melamine/Pt(111). Melamine was coordinated to Pt via two N lone pairs on NH2 and N- in the triazine ring, resulting in a chemisorption structure with slight electron transfer. Four types of adsorption structures were identified: three-point adsorption (two amino groups and a triazine ring: Type A), two-point adsorption (one amino group and a triazine ring: Type B), two-point adsorption (two amino groups: Type C), and one-point adsorption (one amino group: Type D). The most stable structure was Type B. However, multiple intermediate structures were formed owing to the conformational changes from the most stable to other stable adsorption structures. The resonance structures of the adsorbed melamine stabilise the adsorption, as increased resonance allows for more electron delocalisation. In addition, the lone-pair orbital of the amino group in the adsorbed melamine acquires the characteristics of an sp3 hybrid orbital, which prevents horizontal adsorption on the Pt surface. We believe that understanding these adsorption mechanisms will help in the molecular design of organic molecule-decorated Pt catalysts and will lead to the reduction of Pt usage in PEFCs.

First-principles study of adsorption and sensing properties of Re and Tc-doped gallium nitride nanotube (GaNNT) for oil-dissolved gases

In this study, the density functional theory (DFT) method at the B3LYP-GD3BJ/def2svp level of computation was employed to elucidate the adsorption properties of oil-dissolved gases; ethyl (C2H2), methane (CH4), and hydrogen (H2) gas molecule on pure, rhenium (Re), and technetium (Tc) doped GaNNT. The results of the frontier molecular orbitals shows that the doping of Re and Tc on GaNNT surface increases the conductive and sensitivity properties of the surfaces towards the adsorption of investigated gas molecules. The Re doped on GaNNT (Re@GaNNT) surface enhances the stabilization of the donor and acceptor orbitals before and after the adsorption of the considered gas molecules. The DOS of each of these materials is influenced by the presence of dopants Re and Tc. The Re and Tc atoms significantly influenced the energy level in the DOS for the surfaces and complexes. The adsorption of gas molecules on GaNNT and its doped counterparts were analyzed and compared by calculating the adsorption energy of each structure to obtain the most stable adsorption structures. We calculated the adsorption energies and found that CH4 adsorbed positively in all systems, but H2 adsorbed more effectively on GaNNT with an Eads of −0.008 eV. Positive values for weak adsorption are the outcome of other adsorptions. Additionally, all systems experienced substantial adsorptions following the complexation of C2H2. The equivalent Eads for C2H2GaNNT, C2H2Re@GaNNT, and C2H2Tc@GaNNT are –32.550 eV, –32.061 eV, and −31.685 eV, respectively. GaNNT, on the other hand, is believed to adsorb C2H2 better than other systems, with an Eads of 32.550 eV. GaNNT is a better adsorbent for C2H2 and H2 with high and negative Eads, but it is inappropriate for CH4 sensing due to the weak adsorption and minimal conductivity change.

Effect of surfactant compounding on the wettability of talcum powder

AbstractTalcum powder is one of the leading causes of pneumoconiosis, adding compound surfactants to the dust removal process can significantly increase the effectiveness of the dust removal. Therefore, it is of great significance to study the effect of compound surfactants on the wettability of talcum powder. This paper focuses on the ability of compound surfactants to increase the wettability of talcum powder surface by using Materials Studio 8.0. The simulation results were analyzed from the water adsorbed amount, interaction energy, and water molecule concentration profile. Combined with the experimental data of contact angle, the optimal surfactant compounding method was obtained. The simulation results revealed that stable adsorption structures can be formed by the compound of anionic and nonionic surfactants, which can reduce the electrostatic repulsion between anionic surfactants effectively and promote the directional arrangement of nonionic surfactants on the talcum powder surface. When the molar ratio of sodium dodecyl sulfate (SDS) and Polysorbate 80 was 0.4:0.6, the amount of absorbed water reached 113, which is better than monomers and other compound surfactants. The contact angle experiment results indicated a consistent variation law with the simulation results. The contact angle decreased from 68.48° to 19.84° using the compounding method mentioned above, which has the optimum wetting effect among the four compounding methods. The research results will provide a reference for the application of compound surfactants in talcum powder dustproof work.

Study on Corrosion and Wear Behavior Mechanism of Reactor Material in Metastannic Acid Synthesis

AISI 316L, Ti2, and Zr1 are widely used in the selection of reaction still material, however, there is corrosion wear behavior in the use process. In this paper, the adsorption behavior of oxygen in Fe, Ti, and Zr is studied by the first principles method. Corrosion and wear behaviors of AISI 316L, Ti2 and Zr1 were studied by electrochemical corrosion and wear tests. The results show that AISI 316L can effectively resist the action of friction pair during wear by elastic modulus calculation. Oxygen is easily adsorbed at the top of the Fe(111) crystal plane and the bridge site of the Zr(110) crystal plane to form the most stable adsorption structure. The Ecorr of Zr1 (0.275 V) is greater than that of Ti2 (0.266 V) and AISI 316L (0.094 V), resulting in a ZrO2 passivated film with strong protection in the HNO3 solution. The wear rate of AISI 316L is higher than that of Zr1 and Ti2. In the selection of tin chemical reactor material, it is preferred that Zr1 can withstand corrosion and wear for a long time in a nitric acid system, which provides important guidance for corrosion and wear of reactor materials in the synthesis of tin acid.

Theoretical Study of Hydrogen Production from Ammonia Borane Catalyzed by Metal and Non-Metal Diatom-Doped Cobalt Phosphide.

The decomposition of ammonia borane (NH3BH3) to produce hydrogen has developed a promising technology to alleviate the energy crisis. In this paper, metal and non-metal diatom-doped CoP as catalyst was applied to study hydrogen evolution from NH3BH3 by density functional theory (DFT) calculations. Herein, five catalysts were investigated in detail: pristine CoP, Ni- and N-doped CoP (CoPNi-N), Ga- and N-doped CoP (CoPGa-N), Ni- and S-doped CoP (CoPNi-S), and Zn- and S-doped CoP (CoPZn-S). Firstly, the stable adsorption structure and adsorption energy of NH3BH3 on each catalytic slab were obtained. Additionally, the charge density differences (CDD) between NH3BH3 and the five different catalysts were calculated, which revealed the interaction between the NH3BH3 and the catalytic slab. Then, four different reaction pathways were designed for the five catalysts to discuss the catalytic mechanism of hydrogen evolution. By calculating the activation energies of the control steps of the four reaction pathways, the optimal reaction pathways of each catalyst were found. For the five catalysts, the optimal reaction pathways and activation energies are different from each other. Compared with undoped CoP, it can be seen that CoPGa-N, CoPNi-S, and CoPZn-S can better contribute hydrogen evolution from NH3BH3. Finally, the band structures and density of states of the five catalysts were obtained, which manifests that CoPGa-N, CoPNi-S, and CoPZn-S have high-achieving catalytic activity and further verifies our conclusions. These results can provide theoretical references for the future study of highly active CoP catalytic materials.